The invention relates to counting of aerosols or particles and sorting them according to either size, mass or energy. Previous devices for performing this function include optical devices such as those employed in light-scattering counters (Royco Counter) the nethelometer, and LIDAR back-scattering; impactors and collectors employing films or filters to collect quantities of particles or aerosols which can be subsequently weighed and analyzed; and quartz crystal mass monitors which provide mass accumulation data in real time.
The disadvantages of the optical devices are that they depend upon light-scattering thereby making it difficult to get a size distribution without knowing the index of refraction of the scattering centers as well as their shape. Common practice is to assume these scattering centers are spherical which simplifies the interpretation but also introduces errors, the magnitude of which are not really known for most particulate samples. The signal-to-noise ratio for the mechanical collectors and impactors has been low and what has been measured is generally an integrated mass loading. Improved processing of the output from the quartz crystal mass monitors may alter this limitation but such variables as particle adherence and loss to the sampling chain continue to constitute errors in practice.
It is the object of this invention to provide a device for counting of aerosols or particles in real time and sorting them according to their size, mass or energy that is simple, inexpensive and does not have the disadvantages of the prior art devices.